Antigen-based therapies (ABTs) for autoimmune disease are theoretically appealing because they can induce regulatory responses with little interference with immune system function. While ABTs effectively prevent type 1 diabetes (T1D) in NOD mice, ABTs have little to no ability to slow disease progression after NOD mice develop mild hyperglycemia. Moreover, in human clinical trials, ABT's have thus far not shown a significant ability to preserve residual insulin production in individuals newly diagnosed with T1D. Therefore, there is an urgent need to further develop ABTs in combination with other safe therapeutics to better protect remaining ss-cells in newly diabetic animals. In particular, it willbe critical to reduce inflammatory autoimmune responses, promote regulatory responses and promote ss-cell restoration. We propose a safe combination therapy which achieves all these aims. The activation of immune cell g-aminobutyric acid (GABA) receptors (GABA-Rs) has been shown to prevent T1D, experimental autoimmune encephalomyelitis (EAE) and rheumatoid arthritis in mouse models. Based on GABA's ability to inhibit inflammatory responses in different autoimmune diseases and its excellent safety profile, we tested the ability of combined ABT and GABA therapy to preserve syngenic islet grafts mice in diabetic NOD mice, as well as to reverse hyperglycemia in newly diabetic NOD mice. We found that in combination, these treatments act synergistically to prolong ss-cell survival in diabetic NOD mice. Our pilot studies suggest that the activation of GABAA-Rs on T cells also offers a new pathway to promote Treg expansion in vivo. Moreover work from our other studies demonstrate that GABA protects ss-cells from oxidative stress-induced apoptosis and promotes hyperglycemia-induced ss-cell replication. Thus, ABTs and GABA treatments are expected to work by mechanisms that are independent and mutually complementary. We will test the ability of different ss-cell antigens+GABA to reverse hyperglycemia in newly diabetic mice and determine the mechanisms by which ABT+GABA reverses T1D in NOD mice. We will test the hypotheses that 1) combined ABT+GABA treatment inhibits Th1 responses and promotes regulatory T cell responses and 2) that ABT+GABA treatment promotes ss-cell replication. Additionally, because little is known about the biology of GABA-receptors on immune cells, we will characterize GABA-receptors on different immune cell populations and how activation of GABA-Rs affects stimulation-mediated intracellular signaling. These studies will provide the preclinical information needed to initiate clinical trials of a combined therapeutic strategy that s urgently needed given the failure of monotherapies to preserve residual insulin production in newly diabetic individuals. We also expect to identify new pharmacological approaches to help expand Tregs and modulate effector T cells and APCs in ways that will be beneficial for inhibiting T1D as well as other T-cell mediated autoimmune diseases.